High voltage (HV) electrical distribution systems typically use utility poles or towers that support insulators, such as ceramic insulators, and the insulators support conductors that carry the high voltage. A wooden pole is provided as an example in FIGS. 1 and 2, but the structure may instead be a large steel tower for higher voltage transmission.
FIG. 1 is a side view of a top portion of a wooden pole 10, looking into the ends of two horizontal crossarms 12 and 14. FIG. 2 is a top down view of the pole 10 of FIG. 1 showing four sets of insulators supporting four conductors. The crossarms 12 and 14 are typically wood, but materials other than wood are also used for crossarms. In another example, the pole 10 may support only a single insulator and conductor.
Ceramic insulators 16 and 18 are affixed to the crossarms 12 and 14 by bolts 20. A conductor 22 (typically twisted wire strands) seats in a groove in the insulators 16/18 or in some other securing feature, such as a metal vice or other clamp at the top. The conductor 22 is frequently affixed over the top of each insulator 16/18 or to the side of the insulator 16/18 via a metal tie wire.
FIG. 3 illustrates the conductor 22 seated in a top groove 24 of the insulator 16, and FIG. 4 illustrates the conductor 22 seated in the neck 26 of the insulator 16 below the ear 28. The wire tie is not shown.
The crossarms 12/14 in FIG. 2 are shown supporting additional sets of insulators supporting additional conductors for 3-phase voltages. The invention is applicable to all types of insulator configurations.
Dielectric insulator covers, which also cover a portion of the conductor 22, are frequently used for the protection of wildlife and preventing outages, permanent or momentary. The insulator/conductor covers are typically required to be 72 inches in length according to the Suggested Practices Guide developed by the Avian Power Line Interaction Committee (APLIC). Insulator/conductor covers measure 36 inches in one direction from the center of the insulator and 36 inches in the other direction. To obtain this 72 inch coverage, manufacturers have been designing these covers in three separate parts: the insulator cover, one extension arm connectable to one side of the insulator cover, and a second extension arm connectable to the other side of the insulator cover.
Prior art insulator covers for covering the insulators 16 and 18 in FIGS. 1-4 are typically designed for the symmetrical insulator/wire configuration of FIG. 3, where the conductor 22 is tied to the top of the insulator 16. If a prior art cover were used with the asymmetrical configuration of FIG. 4, the cover would seat at an angle over the insulator 16. The cover is somewhat larger than the insulator, so there is some play between the cover and insulator.
Additionally, different conductor diameters may be used with the same type of insulator, where the diameter may be selected based on the required voltage or current transmitted or the distance between poles 10. This further creates unpredictability in the insulator cover's ability to be properly oriented with respect to the insulator and conductor.
In either the symmetrical or asymmetrical case, the prior art covers are not strongly secured to the insulator 16 and conductor 22, and a high wind may catch the open underside of the cover and rotate it with respect to the insulator 16 and conductor 22, reducing the effectiveness of the cover in protecting wildlife and preventing shorts. If a rotated or tilted cover is spotted, a lineman must reorient the cover. The problem with tiled covers is more extreme when the conductor is tied to the side of the insulator, as shown in FIG. 4. In FIG. 4, the rotation point of the cover may be around the off-centered conductor, so the cover more easily lifts off from the opposite side. This exact problem with prior art insulator covers has been reported to the present inventor by a power company, and the inventor was asked to design an improved insulator/conductor cover that did not rotate with high winds.
Therefore, what is needed is a practical cover system for an insulator/conductor that can accommodate symmetrical and asymmetrical insulator/conductor configurations and which cannot be rotated or even tilted when subjected to high winds.